The present invention relates to a method and apparatus for controlling heating and cooling of a transfer unit, which is applied to a precision hot press device capable of highly flat and microstructure transfer, and is particularly applied to a microstructure transfer mold and a microstructure transfer device. The microstructure transfer mold and microstructure transfer device press an original plate (microstructure transfer mold), which is formed with a fine rugged pattern on the surface thereof and serves as a transfer source, against a substrate (transferred body) to which the pattern is transferred, thus transferring and forming the fine rugged pattern on the surface of the substrate. More particularly, the present invention relates to a method and apparatus for controlling temperatures of the transfer unit that enables quick heating and cooling during a microstructure thermal transfer process.
For a thermal nano imprint device for performing the foregoing microstructure thermal transfer, a relatively-inexpensive nano-level imprint device is currently on the market. The microstructure transfer device is capable of nano-level transfer, and is generally referred to as a nano imprint device. The transfer unit of the nano imprint device comprises various functions. The best example thereof is heating and cooling functions. Here, the transfer unit requires a submicron-level of surface precision. Therefore, typically, each mechanism for implementing the heating function and cooling function is integrally molded with the transfer unit.
Heating and cooling are essential for the thermal nano imprint device in order to perform the thermal transfer. In performing the thermal transfer, capabilities to control temperatures highly precisely and uniformly, and to perform heating and cooling quickly are necessary. Here, heating mechanisms include one that employs a heater such as a heating wire, a lamp, or an electromagnetic induction. Cooling mechanisms include one that flows a cooling medium (e.g., water, gas, and oil) in a cooling path, or a means for putting the heating and cooling mechanism itself in a cooling chamber. As a specific example of the heating mechanism and cooling mechanism, a scheme is used that flows a heating medium or a cooling medium through a block body (heater plate) which is configured to be attached with a heating source or a cooling source. Typically, for the temperature control of the heating and cooling mechanism, a programmable air conditioner is employed that is commercially available. Some temperature control technologies, which are not limited only for the thermal nano imprint device, are disclosed in JP-A-2002-157024 and JP-A-2005-329577.
The temperature control scheme disclosed in the patent documents or the temperature control employing a commercially available programmable air conditioner typically measures a change in temperature from a current temperature to a target temperature as well as a time required to reach the target temperature, and controls a heating output and a cooling output based on the result of the measurement. These temperature control schemes are capable of controlling temperatures highly precisely. However, since these schemes perform the temperature control from a change in temperatures, there arises a time lag between the temperature measured after heat is transferred and controlling of output. This is because of the quality of the material and cubic volume of the heating and cooling mechanism. As a result, the heat output is more suppressed as the current temperature gets closer to the target temperature, thus making it difficult to perform quick temperature control.
As for the thermal nano imprint device, there is one that is earlier proposed by the present applicant in a patent application No. 2008-262699. FIG. 5 is a cross-sectional diagram representing an example of the thermal nano imprint device as a precision press device. Basically, the thermal nano imprint device comprises: a pressure receiving portion 511 which is fixed to one end each of a plurality of (three or four in this case) guide posts 514a, 514b (hereinafter collectively referred to as 514. Other components are also referred to in the same collective manner) that are disposed in parallel with each other; a pressure portion 512 disposed to oppose the pressure receiving portion 511 and to be able to move toward and away from the pressure receiving portion 511 by sliding on the guide posts 514; and a drive portion 518 for driving the pressure portion 512 towards the pressure receiving portion 511 via a free bearing 519. The pressure portion 512 and drive portion 518 are not bolt-fixed. Instead, they are attached to be somewhat rockable like a stripper bolt, a damper, or a spring, and are placed on the free bearing 519. For a drive source of the drive portion 518, a servo motor, an air cylinder, a hydraulic cylinder, and the like can be used.
The pressure receiving portion 511 is fixed to the guide posts 514 by adjustable nuts 513. The adjustable nuts 513 are capable of adjusting the mounting height of the pressure receiving portion 511 relative to the guide posts 514 in the level of 1/100 mm during assembly. Even after assembly, the adjustable units 513 are capable of adjusting the flatness of the pressure receiving portion 511 in the nano level. Thus, the pressure receiving portion 511 is uniformly guided by the guide posts 514.
The pressure portion 512 is disposed to be able to slide on the guide posts 514 via retainers 515 and elastic bodies 516. The cylindrically shaped elastic bodies 516 made of urethane resin are fixed in such a manner that they are fitted into sliding holes formed on the pressure portion 512. A direct-acting guide bearing formed into a cylindrical shape or the like, for example, can be used for the retainers 515 which are fitted into the cylindrical interior of the elastic bodies 516, thus making it possible to exhibit high precision alignment until a forming die contacts an object to be transferred. The elastic bodies 516 are provided with flange portions on one end side thereof, which abut the upper surfaces of the pressure portion 512. The retainers 515 are provided with flange portions on one end side thereof, which abut the flange portions of the elastic bodies 516, thus each being positioned in the axial direction. The retainers 515 are slidable on the guide posts 514 which are inserted into the cylindrical interiors of the retainers, and, as a result, the pressure portion 512 is slidable on the guide posts 514 via the retainers 515 and elastic bodies 516.
The pressure receiving portion 511 and pressure portion 512 are provided with press stages 517a, 517b, respectively, on their surfaces opposite to each other. A micromachined original plate is disposed on one surface of each of the press stages 517a, 517b, and a substrate is disposed on the other surface of each of the press stages 517a, 517b. During a pressing process, the original plate is pressed against the substrate. As a result, a micromachined pattern of the original plate is transferred onto the substrate. The press stages 517a, 517b, which support the original plate or the substrate, constitute a transfer unit having a heating and cooling mechanism for heating or cooling the original plate or substrate.
The elastic bodies 516 installed to the guide posts 514 are members for adjusting the flatness to a nano level during a pressing process. The elastic bodies 516 are configured to retain an entire ram of the pressure portion 512, and thereby to retain the press stage 517b or the entire pressure portion 512, absorb the inclination and deflection of the pressure portion 512, such that the pressure portion 512 follows the pressure receiving portions 511.
When the present precision hot press device operates, the drive portion 518 for driving the pressure portion 512 presses the pressure portion 512 via the free bearing 519. A tip of the free bearing 519 is spherically shaped, and, when the press device operates, the pressure portion 512 follows the pressure receiving portion 511. That is, even if the press stages 517a, 517b, which will be described later, follow each other due to the elastic deformation of the elastic bodies 516, it is possible to apply a load to the pressure portion 512 at a single point. During a pressing process, the elastic deformation of the elastic bodies 516 absorbs relative inclination and deflection of the pressure receiving portion 511 and pressure portion 512. As a result, following condition between the pressure receiving portion 511 and the pressure portion 512 is maintained, and the press stage 517 is uniformly loaded, thus making it possible to perform press molding precisely enough to achieve a high-flatness.
Elimination of an influence of heat accumulated in a plastic mold is proposed in JP-A-08-332637. According to the proposition, the influence is eliminated by using a non-contact temperature sensor that is disposed near the surface of the metal mold, and by setting the mold and a noncontact air as a reading point in a plastic mold that uses a metal mold. A method of quickly and precisely controlling the temperature on the surface of a metal mold is proposed in JP-A-11-291300. According to the proposition, the quick and precise temperature control is achieved by directly incorporating a temperature detection sensor within a mold surface material layer of a metal mold and by bringing the temperature detection sensor as close as possible to the surface of the mold thereby to unify it with the mold surface material layer in a plastic injection mold employing a metal mold for plastic injection molding. Furthermore, a method of controlling to cool the temperature of a metal mold, before it is injection-molded, to a solidification temperature is proposed in JP-A-2009-45814. According to the proposition, it is achieved by changing a heating heat medium from water vapor, which is originally used, to high-temperature water, and subsequently changing it to cooling water after the injection.
As explained in the above, in the precision hot press device, as a microstructure transfer mold and a microstructure transfer device for transferring and forming fine rugged patterns on the surface of a substrate, the substrate is softened during the transferring and forming of the rugged pattern, and after the transfer, the substrate is cooled and thereby the rugged pattern is hardened and finalized. In order to enhance the productivity of the microstructure transfer of the precision press device, it is necessary to perform the heating and cooling of the transfer unit, which is repeatedly conducted by the heating and cooling mechanism, as rapidly as possible. In reducing the time required to heat and cool the transfer unit in the precision hot press device, as much as possible, there are some problems to be solved concerning the management of entrance and exit of heat conducted by the heating and cooling mechanism.